How to properly wipe an Android device

by: Edgar CervantesMarch 16, 2016

Android Lollipop Nexus 7 factory reset restoring

Is it time to clear your smartphone? Maybe you want to sell it or give it away to someone. The smartest thing to do is wipe the device clean and get it back to factory settings. But did you know a traditional factory data reset won’t take care of the job 100%?

Much of your personal data will survive a wipe, but it will pretty much be hidden. Regardless, there are plenty of tools out there that would allow any new owner (or thief) to easily retrieve this information. In this post we show you how to really take care of the situation and make sure all your sensitive information is safe from sneaky tinkerers.

SecurityKnox New York Post

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Understanding how storage is handled

Surely, you have seen all these services and programs that promise to recover lost data. This is totally possible, and it’s because of the way most operating systems (including Android) handle storage.

No file is ever really gone when you hit the ‘delete’ button. It just becomes invisible to the user and marked as “free space”. Then it is left chilling in the background until the system needs the space again. New files then replace the older ones.

Why even do this? There are a few reasons why this method is convenient. For starters, truly deleting documents from a drive can take a toll on the hardware. Remember HDDs and even SSDs have an estimated lifespan, and after so many rewrites they wear out. By marking a file as “deleted” but not removing it completely, you reduce the amount of times modifications have to be made.

delete-sms-text-message Shutterstock

In addition, slower hardware really used to benefit from this. This is because it was much faster to mark a bunch of files as invisible, as opposed to actually deleting them. Storage is super fast these days, but it probably still helps a bit. Plus, this happens to be a life saver those times when you accidentally delete valuable data.

How to properly wipe an Android phone

There’s no direct way to really wipe a device all the way, but we can show you how to at least keep your important data safe. Let’s get started.

Encrypt your phone

If all your stuff is going to stay within your storage after a factory data reset, you should at least make sure no one can take advantage of it. Encrypting your device won’t stop the software from going through it’s usual deleting process, but any information retrieved from the device will be scrambled. People won’t be able to do a thing with it.

Simply go to the Settings app and select ‘Security’. From there you can scroll down and hit the “Encrypt phone” option. It’s super simple. But beware that steps may vary a bit depending on your phone. These steps are for stock android Marshmallow.

Once your phone is encrypted, simply perform a factory data reset the way you normally would.

Load the phone with trivial files

Still want to get rid of all that personal information stored deep within the guts of the phone? It will only be deleted once it is replaced with other files, so the solution is simple. Just load a bunch of files in there!

Of course, you want these to be files that don’t matter. Or at least stuff you wouldn’t mind others getting a hold of. These could be songs, movies, photos or anything. Just fill up your smartphone’s storage as much as possible. After that, perform another factory data reset and intruders will only be able to retrieve the dummy data.

phone-storage Shutterstock

Wrapping up

As we mentioned above, this is more a workaround than it is a solution. This is the closest we can get to a proper phone wipe… without going too crazy. How else would you keep your private information safe? Hit the comments and let us know.

  • Joshua

    sounds like a great idea

  • Jorge Alan Gonzalez Barrón

    TWRP and some custom CWM recoveries hace a shred function, that will fill your storage with 0’s or 1’s

  • FirefoxGuru

    Hmm, didn’t know ext4 also did this, thought it was Windows (NFTS) only… so why the hell do deletes from the TouchWiz gallery or QuickPic take an age for simple photos? I guess different ROMs of Android might handle delete procedures differently.

  • T.J.

    I wonder if someone has created a cache of files to fill a device you can just download.

  • HB.Grizzly

    Some time ago I was looking for an APP doing what under WINDOWS is called the “TRIM” fuction, but could not find anything! Now I have one more reason to search on…
    Some hints about “save erase”:
    1. Encryption will encrypt visible file only – ‘deleted’ files will not be changed!
    2. SD storage works like SSD: overwriting/changing of data is slower then writing to empty blocks!
    => a TRIM would not only “save erase” all deleted data, it would speedup writing (and aging) too!
    3. A fast way to fill up your storage:
    a) create a simple text file (not a .docx => contains creaters data) and type in a line of “U” (binary 01010101)
    b) multiply it by doing a “select all”, copy it, then do some pastes
    c) repeat step b) for the now larger block of text
    d) repeat c) untill you reach max file size, then save it
    e) multiply this file in a directory, then multiply this directory, then multiple the directories…
    (works nice if you use a file manager asking you “replace or save as copy”)
    4) Less save generation of big files: take a HD video in the dark. But it will contain user data too…

    Does anyone know about an ANDROID TRIM?

    • KeyserSoze

      “Does anyone know about an ANDROID TRIM?”

      I could be wrong but I thought Android had TRIM support since version 4.3 Jellybean. I used to run an app called LagFix to manually TRIM the internal storage on my Verizon Galaxy Nexus which didn’t have built-in TRIM support in its older OS.

      • HB.Grizzly

        You are right – a big, big SORRY – it’s there since 2013 with 4.3.
        Thanks for making me spending some hours on reading more about TRIM and SD/SSD/NAND and flash memory => today Google showed me quite a lot of info I didn’t find 2 years ago…
        NOW I learned:
        – manual trim on Android for rooted devices only
        – trim works different from what I thought => NO erase of data and NO aging
        ==>> filling up all free space with U’s is a bad idea, it even helps hackers to sort out garbage from juvels

        I have to edit my comment!

  • WAusJackBauer

    I thought factory resetting your phone twice did the job. Can anyone confirm?

    • zuckerj

      No, as the article describes, it is still there if you are really interested in getting at it.

  • Goblin Shark

    Thank you for this information.